Production of fatty acids is carried out by hydrolyzing oil and fat. High pressure and temperature hydrolysis (JP-A-2003-113395) or enzymatic hydrolysis (JP-A-2000-160188) is employed as a method of hydrolyzing oil and fat. The former method is performed under high temperature and pressure conditions in the presence of water and has an advantage of high productivity. However, when a raw material containing a large amount of unsaturated fatty acid is used in this method, a large amount of trans-unsaturated fatty acid is produced depending on the conditions in some cases. On the other hand, the latter method is performed under reaction conditions having a low temperature of 0 to 70° C. in the presence of an enzyme such as lipase as a catalyst, and as a result, this method has low productivity compared to the high pressure and temperature hydrolysis method although no trans-unsaturated fatty acid is produced.
Further, high pressure and temperature hydrolysis has an induction period at an initial stage of the reaction before decomposition starts. To avoid or shorten the induction time, there is a technique in which glyceride is first partially hydrolyzed by enzymatic hydrolysis using the 1,3-position specific lipase to prepare partially hydrolyzed glyceride, and then high pressure and temperature hydrolysis is performed (JP-A-8-507917).